Guitar Power amp/preamp for Bass?

I am a guitar player exploring playing bass.
A friend is loaning me a bass cab and amp temporarily.

I know using guitar amp is a no no so I plan on buying a dedicated bass cabinet but don't want to buy a bass amp for the moment. But....I am looking to leverage my current gear for bass. Will this help?

The power amp shouldn't be an issue. It won't hurt a guitar preamp any to use it for bass, but the EQ will probably be voiced funny, and it may or may not push enough bottom end to sound good. I can't speak to the specific preamps you've got, but they're certainly worth a try.

There are some cheap bass preamps around, and actually some active basses are hot enough to drive a power amp directly.

IME, all tube Marshall guitar rigs sound great for bass assuming you have the proper cabinet. It's a different sound than you'd get from a system designed for bass but to me it sounds pretty godly. Try it out and switch it up if you need something different.